Some electronic systems utilize redundancy to fulfill safety, functionality and performance requirements. For example, a road-vehicle functional safety standard now under development, ISO 26262, requires varying degrees of redundancy in sensors, processing channels, actuators, interconnections and energy supplies to implement vehicle functionality at various automotive safety integrity levels (ASILs). ISO 26262 seeks to meet safety goals at many phases of the automotive product cycle, including during development, production, operation and servicing of road vehicles. Other standards also mandate redundancy for electronic systems other than road vehicles.
FIG. 1 depicts an embodiment of a redundant analog-to-digital conversion system 20. The system 20 includes two conversion channels, each having a separate analog to digital converter ADCA, ADCB. Each of the converters ADCA, ADCB receives the same analog input A1, and produces a separate corresponding digital output D1, D2 representing the conversion to the digital realm of the received analog input A1.
Such a redundant conversion system 20 needs to be tested to meet safety standards. FIG. 2 depicts an embodiment of a method 40 of testing the conversion system 20 of FIG. 1. In a first step 42, a particular value of the analog input A1 is provided to the first and second converters ADCA, ADCB. At a second step 44, the output D1 of the first converter ADCA is evaluated. This evaluation can include various sub-steps, such as determining if the output D1 is the correct digital code to correspond to the particular analog input value, and determining whether the digital output D1 meets other performance measures in relation to previous digital output values, such as measures related to linearity, offset error, gain error, signal-to-noise ratio, total harmonic distortion, etc. At a third step 46, the digital output D2 of the second converter ADCB is evaluated. This evaluation can also include various sub-steps, such as those identified above.
The conversion system 20 and test method 40 of FIGS. 1-2 have shortcomings, however. Foremost among these is the fact that each of the converters ADCA, ADCB is separately tested to ensure safety. As each of the corresponding evaluation steps 44, 46 can be a time intensive procedure, separately testing each converter ADCA, ADCB can be inefficient in both manufacturing and operational environments. Additionally, the conversion system 20 of FIG. 1 provides no functionality or output signal that is related to the performance and safety status of the redundancy of the system 60, i.e., related to the performance and safety status of both the first and second converters ADCA, ADCB.
Thus, there exists a need for electronic systems that can implement redundancy to meet functionality and safety concerns, but that do not necessarily require full redundancy for testing in manufacturing, operational or servicing environments.